Cre recombinase is expressed from this allele under control of the endogenous Fgf16 promoter in the developing cristae and spiral prominence epithelial precursors of the inner ear. The Cre recombinase coding sequence, preceded by an internal ribosomal entry site (IRES) and followed by a single frt site (marking the site of excision of a frt-flanked neomycin resistance cassette), interrupts the first exon of Fgf16 so that codon 63 is disrupted.